1. Field of the Invention
This invention relates to machine tools.
In a further aspect, the present invention relates to attachments for machine tools.
More particularly, the instant invention concerns a drill actuating mechanism especially adapted for sensitive drilling operations in machine tools.
2. Description of the Prior Art
Various machine tools, including drill presses, milling machines and lathes, are frequently used to perform drilling operations. Commonly, each of the instant type of machine tools includes means for supporting a work piece and means for holding the shank of a boring tool, such as a twist drill. Rotation is imparted to either the work piece or the boring tool. Further, the machine tool includes means for axial reciprocal movement of the boring tool relative the work piece.
In a drill press, the machine tool especially devised for conducting drilling operations, the work piece is supported upon a table. Positioned above the table, and usually perpendicular thereto, is a reciprocally movable cylindrical element referred to as a quill. Carried within the quill is a spindle which is rotatably driven by a motor. Provided at the lower end of the spindle are means for holding the shank of a twist drill or other boring tool such as a counterbore or countersink. Typically, the means for holding the boring tool is in the form of a drill chuck. In accordance with conventional practice, the quill is reciprocally moved by a rack-and-pinion mechanism in response to an operator manipulated handle.
A milling machine, in general similarity to a drill press, typically includes a horizontal work supporting table and an upright quill. The spindle is generally provided with a collet arrangement for holding the shanks of various cutting tools. On occasion, twist drills are held directly by the collet. More frequently, however, twist drills are held by a drill chuck, the shank of which is held by the collet.
While the method of drilling in a lathe is substantially equivalent to the procedure involving a drill press or milling machine, the components are somewhat different. The work piece is generally held and rotated by a face plate or chuck carried by a horizontal spindle within a headstock affixed to one end of an elongate bed. A tailstock, slidably along the bed, carries a reciprocally movable quill. A drill chuck is attachable to the quill for purposes of performing drilling operations.
The drilling operations performed in various machine tools are generally analogous. During relative rotation between the drill and the work piece, the drill is moved axially with controlled pressure to enter the work piece. The rate which the drill moves is termed the rate of feed. A cutting lubricant is usually applied to the drill during the cutting operation. Periodically the drill is withdrawn from the hole being bored for the purpose of removing chips and also for the further application of cutting lubricant.
The effort or force exerted by a machine tool operator to feed a drill is variably dependent upon the size of drill and the hardness of the material of the work piece. In general, the larger the drill and the harder the material, the greater the force required. Conversely, relatively little effort is required to urge a comparatively small drill into soft material. Machine tool operators subjectively judge the proper note of feed by the traditional and familiar method known in the art as "feel".
In addition to the force required to urge the drill into the work piece, the operator of a machine tool is required to exert additional force to impart movement to the massive components of the machine and overcome internal friction. Accordingly, machine tools have not proven to be entirely satisfactory for all drilling operations. This is especially acute in situations involving relatively small drills and further complicated by comparatively hard materials. The "feel" of the drill is lost. That is, the force required by the drill is negligible and cannot be distinguished by the operator in comparison to the force required to move the components of the machine. Resultingly, small drills are frequently broken and holes thus drilled are not true.
In recognition thereof, the prior art has provided sensitive adapters for use in machine tools for the express purpose of drilling small holes. A small hole is loosely defined as one made by a drill in the number size range, 0.0135 inch to 0.228 inch. Exemplary is the sensitive precision drill adapter distributed by the H. C. Stanley Company. The device includes a stem coaxially, slidably mounted within a sleeve. At the free end of the stem, extending from the sleeve, is a chuck especially adapted for holding small drills. A feed ring in the form of a collar is rotatably journaled on the stem intermediate the chuck and the sleeve. The drill chuck has a variable capacity of 0.000 inch to 0.156 inch.
During use, the sleeve is held within the chucking means, large drill chuck or collet, of the selected machine tool. The operator manipulates the drill by manually holding the feed ring. It is noted that the stem is not rotatable relative the sleeve. Accordingly, the operator is not concerned with the internal friction nor mass of the machine tool. During the drilling of small holes, it is preferred method among those skilled in the art that the operation is performed with numerous successive reciprocal movements. During each inward movement, the drill is advanced into the material a relatively small amount, perhaps as much as a few thousandths. During withdrawal, chips are removed from the drill and lubrication is applied thereto.
Drill adapters of the foregoing type, while nullifying the internal friction and weight of the machine tool, have not presented an entirely satisfactory solution to the problem of drilling small holes. Considerable operator pressure must be applied for drilling holes larger than approximately one-half of the capacity of such adapters. Manipulating the relatively small feed ring has proven to be a cumbersome and tiring procedure. Further, difficulty is encountered during drilling operations which require rapid or repeated reciprocal movement of the drill. Other shortcomings will be apparent to those skilled in the art.
Accordingly, it is an object of the present invention to provide improved means for drilling small holes.
Another object of the invention is the provision of a sensitive drill actuating mechanism.
And another object of the invention is to provide an attachment which is readily usable with various machine tools.
Still another object of this invention is the provision of improved means for actuating a conventional sensitive drill adaptor.
Yet another object of the invention is to provide means for decreasing the effort required when utilizing drills in the larger range of the capacity of drill adapters.
And still a further object of the invention is the provision of a drill actuating mechanism which is detachably securable to the machine tool and the drill adapter.
A further object of the instant invention is to provide a drill actuating mechanism which will easily facilitate rapid and repeated reciprocal movement of the drill.
And a further object of the invention is the provision of a device which is easily usable and will substantially reduce operator fatigue.
And still a further object of the invention is to provide a sensitive drill actuating mechanism which will not interfere with the operator's feel of the drill.
And still a further object of the invention is the provision of a device of the above type which is free of delicate components and relatively durable.